At the time of the 1953 census, the Piro of the Urubamba were seminomadic, and their thirteen villages ranged in population from 4 to 125. The 1981 census showed sixteen villages with populations ranging from 6 to 259 inhabitants each; village life had become stabilized. Usually Piro villages extend along the rivers. Sites are chosen with highwater season in view, since the level of the Urubamba varies as much as 8 meters from dry season to rainy season. All of the large trees are cleared from a village site, and the areas immediately surrounding the houses are periodically scraped clean with machetes. Houses are typically rectangular with woven palm-thatch roofs and palm-bark sleeping platforms. Formerly the houses were without walls, but with the increase of population and of visits from outsiders, some families now build walls of cane, palm bark, or undressed boards. Tools, nails, and boards are not uncommon now, whereas the jungle formerly supplied all materials used in the construction of the house and its furnishings. Nearly every village has one structure that serves as a church. The larger villages have well-kept soccer fields. Plantings surround the village. Acquisition of land titles has made it necessary to extend the duration of villages beyond the ten to fifteen years characteristic of slashand-burn agriculture.